Solar problems. Please help!

Re: Solar problems. Please help!

If the Solar Charge Controller is a standard PWM controller--then the fact that the panels were about the same voltage as the batteries indicates that the charge controller appropriately (directly connecting the solar panels to the battery to charge).

At this point, if possible, you should bring a DVM, generator, and battery charger to the cabin.

First, measure the current output by your solar panels during full sun--should be near their Imp rated voltage. Next, you should disconnect the solar panels from the charge controller and check for a current path (lights left on, something plugged in, and also check if the solar charge controller is draining the battery bank).

If you find the problem or not, next you should but the battery bank on charge and get it up to at least 75% state of charge (if you have time, fully charge the bank). You can use a hydrometer to check all of the cells--if you find one or two cells that are very high or very low wrt to the others--then you may have a bad battery (shorted cell can discharge the entire bank--open cell can prevent string from charging) or cable/connection.

In any case, the longer you let the batteries set at 75% or less State Of Charge--the more the batteries are being damaged/ruined (sulfates in a discharged battery begin to harden within a few hours when below ~75% state of charge).

If the batteries set at 9 volts until next weekend--there is a good chance that you will need to replace them (assuming that the solar charger is not working properly or the unknown load / bad cable / bad battery has not been fixed).

-Bill

Re: Solar problems. Please help!

One possible reason for the "crash"... If you have been running deficit charging (not fully charging the batteries after every use)--it is possible that you have been charging 10% less every trip--and the last one took your batteries from 10% charge to 0%...

You did not give the size of your solar panels and other specifics--Another reason to check the state of charge of your battery bank once in a while--to make sure that they are getting 100% charged (and equalized with flooded cell batteries) at least once in a while.

Many systems (not saying yours) end up with deficit charging and the owners don't realize it for months or until the weather turns bad or more visitors come by and burn more power than normal.

-Bill

Re: Solar problems. Please help!

The 13 volts when you got there--really depends if the batteries were "resting" for several hours or if that was with sun on the panels and "charging".

If that was 13 volts "resting" (still dark in the morning), then this is actually "over" 100% charge (12.7 volts at 77F).

If this was 13 volts at 10am-12noon... Then it is possible that this indicates the batteries are not charging sufficiently (current flowing through the controller).

If this was 13.02 to 13.20 volts, and you have a 3+ stage controller with a "float" setting, then this could indicate that the solar charge controller thought that the batteries where fully charged.

For random (maybe a couple times a month), a hydrometer and thermometer would tell you very quickly if the battery bank was fully charged or not--regardless of the load/charge currents and/or time of day. The first time you check your battery bank, you should measure (and log) the specific gravity of all cells/batteries to ensure that they are tracking closely together... If not, then you should check for improper or bad wiring, or possibly, one or more failed cells.

Personally, I really like the Battery Monitor type devices... They are the closest you will get to a "battery bank fuel gauge" short of using a hydrometer multiple times a day. The older Xantrex XBM was recommended by a few people here--and I like the looks of the Xantrex LinkLite and LinkPro meters (I have not used any of these products). However--not everybody can justify the $200-$400 these things cost.

Regarding the Inverter Shutdown... Typically, these are set to around 10.5 volts or a bit less... This voltage setting, in my humble opinion, is not set to protect the battery, but instead to protect the inverter itself attached loads)....

Since Inverters are constant power devices (for a set load, say 100 watts and 80% efficiency=>120 watt load at 12 vdc; at 14.5 volts the inverter will draw 8.3 amps; and at 10.5 volts it would draw 11.4 amps) to prevent it from drawing too much current and burning itself out, and to prevent "brownouts" at the AC appliances that are attached to the inverter (which can damage motors and electronic devices).

At 10.5 volts--the battery is 100% dead (assuming no load)--well below the 50% discharge that we normally aim for.

In the end, because during heavy loads/surges you can see the battery voltage / wiring leads drop by several volts (large load relative to the battery bank--such as starting a well pump)--the voltage trip point is usually set pretty low to prevent false triggers (turning off) when trying to start heavy loads.

But, in reality, it is almost impossible to know the battery's state of charge using a volt meter to estimate the state of charge of a battery when under load or under charge... The only time you can use a volt meter is after the battery has rested for 3 hours or so. And the meter needs to be accurate to 100th of a volt--12.xx--volts at least).

The meter should be attached directly to the batteries for accurate voltage measurements--placing the meter on the inverter inputs also takes into account the voltage drop of the cable when the inverter is on and under load... Measuring the voltage at the inverter is OK and accurate if done when the inverter is turned off.

If you need to run the inverter while the cabin is unattended--I would use something like the Xantrex LinkLite which gives you real battery capacity and you can set it to turn off a switch if the battery capacity falls below 50% (or whatever setting you choose).

Setting up a voltage trigger to turn off your inverter is not going to be very accurate because the battery voltage not only changes with state of charge, but if charging/discharging and with temperature changes too.

In the end, I am not saying you are deficit charging--but if you have no other explanation (shorts, something left on, etc.), then you are tending towards deficit charging--either because of to much load, to few solar panels, or a charge controller not properly charging the battery (wrong settings, controller hot while batteries cool, bad wiring, bad controller, one or more open/shorted cells in your batteries, etc.)...

Sorry I can not be more exact in my diagnosis--but it is difficult based on what I know so far.

-Bill

Re: Solar problems. Please help!

The batteries really need to sit (no load/no charging currents) for 3 or more hours before you can accurately measure their charge using a volt meter...

Given it was cloudy--probably did not get much charging that afternoon.

Lastly, you really need to measure the current from the panels when they are (or should be) charging your batteries.

Many solar panel faults are "high resistance" types (corrosion, burned spots, etc.) and with a modern DVM--the meter does not supply enough load for the high resistance to show voltage depression.

-Bill